Gas control system for reflow furnace and reflow furnace

Abstract

The present application discloses a gas control system for a reflow oven, a hearth thereof comprising a preheating zone, a peak zone and a cooling zone. The gas control system comprises: an oxygen detection apparatus, a first valve apparatus, a second valve apparatus and a controller. The controller is configured to control the degree of opening of the first valve apparatus and/or the second valve apparatus when the oxygen concentration detected by the oxygen detection apparatus does not satisfy a preset value, in order to enable the oxygen concentration in the peak zone to satisfy the preset value by adjusting the flow rate of working gas and/or air inputted into the peak zone. The gas control system and reflow oven of the present application first perform rough adjustment of gas in the hearth, such that the oxygen concentration in the hearth is substantially close to the preset value. The oxygen concentration in the peak zone of the hearth is then adjusted precisely by means of the first valve apparatus and second valve apparatus. Thus, even though the amount of oxygen in air entering the hearth is indeterminate, the oxygen concentration of the peak zone will not be affected, so the quality of circuit board soldering can be increased in a stable fashion.

1 . A gas control system for a reflow oven, a hearth ( 112 ) of the reflow oven ( 110 ) containing a gas, the gas comprising oxygen and a working gas, and the hearth ( 112 ) comprising a preheating zone ( 101 ), a peak zone ( 103 ) and a cooling zone ( 105 ), characterized in that the gas control system ( 100 ) comprises:
 an oxygen detection apparatus ( 120 ), the oxygen detection apparatus ( 120 ) being configured to detect the oxygen concentration in the peak zone ( 103 );   a first valve apparatus ( 131 ), the first valve apparatus ( 131 ) being configured to fluidly connect a working gas source ( 140 ) to the peak zone ( 103 ) of the hearth ( 112 ) in a controllable fashion;   a second valve apparatus ( 132 ), the second valve apparatus ( 132 ) being configured to fluidly connect an air source ( 150 ) to the peak zone ( 103 ) of the hearth ( 112 ) in a controllable fashion; and   a controller ( 122 ), the controller ( 122 ) being in communicative connection with the oxygen detection apparatus ( 120 ), the first valve apparatus ( 131 ) and the second valve apparatus ( 132 ); and the controller ( 122 ) being configured to control the degree of opening of the first valve apparatus ( 131 ) and/or the second valve apparatus ( 132 ) when the oxygen concentration detected by the oxygen detection apparatus ( 120 ) does not satisfy a preset value, in order to enable the oxygen concentration in the peak zone ( 103 ) to satisfy the preset value by adjusting the flow rate of working gas and/or air inputted into the peak zone ( 103 ) of the hearth ( 112 ).   
     
     
         2 . The gas control system as claimed in  claim 1 , characterized in that:
 the gas control system ( 100 ) comprises a mixing duct ( 135 ), the mixing duct ( 135 ) comprising a first inlet ( 136 ), a second inlet ( 137 ) and at least one outlet ( 126 ,  127 ), the working gas source ( 140 ) being in fluid communication with the first inlet ( 136 ) via the first valve apparatus ( 131 ), the air source ( 150 ) being in fluid communication with the second inlet ( 137 ) via the second valve apparatus ( 132 ), and the at least one outlet ( 126 ,  127 ) being in fluid communication with the peak zone ( 103 ).   
     
     
         3 . The gas control system as claimed in  claim 1 , characterized in that:
 the peak zone ( 103 ) comprises three secondary peak zones (Z 10 , Z 11 ,  212 ), the three secondary peak zones (Z 10 , Z 11 , Z 12 ) comprising a middle secondary peak zone (Z 11 ) located in the middle and two side secondary peak zones (Z 10 , Z 12 ) located at two sides of the middle secondary peak zone (Z 11 );   the oxygen detection apparatus ( 12 ) is configured to detect the oxygen concentration in the middle secondary peak zone (Z 11 );   the at least one outlet ( 126 ,  127 ) comprises two outlets ( 126 ,  127 ), the two outlets ( 126 ,  127 ) being in fluid communication with the two side secondary peak zones (Z 10 , Z 12 ) respectively.   
     
     
         4 . The gas control system as claimed in  claim 1 , characterized by further comprising:
 a third valve apparatus ( 133 ), the third valve apparatus ( 133 ) being configured to fluidly connect the working gas source ( 140 ) to the preheating zone ( 101 ) of the hearth ( 112 );   the degree of opening of the third valve apparatus ( 133 ) remaining unchanged during operation of the reflow oven ( 110 ).   
     
     
         5 . The gas control system as claimed in  claim 4 , characterized in that:
 the preheating zone ( 101 ) comprises multiple secondary preheating zones (Z 01 , Z 02  . . . Z 09 ) and the working gas source ( 140 ) is controllably in fluid communication with the secondary preheating zone (Z 02 ) that is second-furthest from the peak zone ( 103 ) via the third valve apparatus ( 133 ).   
     
     
         6 . The gas control system as claimed in  claim 4 , characterized by further comprising:
 a fourth valve apparatus ( 134 ), the fourth valve apparatus ( 134 ) being configured to fluidly connect the working gas source ( 140 ) to the cooling zone ( 105 ) of the hearth ( 112 );   the degree of opening of the fourth valve apparatus ( 105 ) being determined according to the preset value.   
     
     
         7 . The gas control system as claimed in  claim 6 , characterized in that:
 the cooling zone ( 105 ) comprises multiple secondary cooling zones (C 01 , C 02  C 04 ), and the working gas source ( 140 ) is controllably in fluid communication with the secondary cooling zone (C 03 ) that is second-furthest from the peak zone ( 103 ) via the fourth valve apparatus ( 134 ).   
     
     
         8 . The gas control system as claimed in  claim 1 , characterized in that: the controller ( 122 ) is configured to:
 determine an adjustment range according to the preset value of oxygen concentration;   
       increase the degree of opening of the first valve apparatus ( 131 ) when the oxygen concentration detected by the oxygen detection apparatus ( 120 ) is greater than the maximum value of the adjustment range, to enable the oxygen concentration to reach the adjustment range by increasing the flow rate of working gas inputted into the peak zone ( 103 ) of the hearth ( 112 );
 increase the degree of opening of the second valve apparatus ( 132 ) when the oxygen concentration detected by the oxygen detection apparatus ( 120 ) is less than the minimum value of the adjustment range, to enable the oxygen concentration to reach the adjustment range by increasing the flow rate of oxygen inputted into the peak zone ( 103 ) of the hearth ( 112 ); 
 adjust the degrees of opening of the first valve apparatus ( 131 ) and the second valve apparatus ( 132 ) when the oxygen concentration detected by the oxygen detection apparatus ( 120 ) is within the adjustment range, so that the oxygen concentration in the peak zone ( 103 ) satisfies the preset value. 
 
     
     
         9 . The gas control system as claimed in  claim 6 , characterized in that:
 the first valve apparatus ( 131 ), the second valve apparatus ( 132 ), the third valve apparatus ( 133 ) and the fourth valve apparatus ( 134 ) are flow control valves.   
     
     
         10 . A reflow oven, characterized by comprising:
 a hearth ( 112 ), the hearth ( 112 ) comprising a preheating zone ( 101 ), a peak zone ( 103 ) and a cooling zone ( 105 ), and the hearth ( 112 ) containing a gas, the gas comprising oxygen and a working gas; and   the gas control system ( 100 ) as claimed in  claim 1 .